Relationships between molecular and plane-stress essential work of fracture parameters in amorphous copolyesters
Relationships between molecular and plane-stress essential work of fracture parameters in amorphous copolyesters
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无定形共聚酯断裂参数的分子和平面应力本质功之间的关系
DOI：
10.1007/s002890050179
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发表时间：
1997
期刊：
影响因子：
3.2
通讯作者：
E. Moskala
中科院分区：
文献类型：
--
作者：
J. Karger‐Kocsis;E. Moskala
摘要
采用拉伸加载的双边深缺口（DDEN - T）试样，通过断裂基本功（EWF）概念测定了不同特性粘度（IV）的无定形共聚酯（aCOP）片材的平面应力断裂韧性。研究发现，比断裂基本功（we）是一个复合参数：其组成部分分别取决于屈服（we,y）和颈缩（we,n）。we值，尤其是we,y，并不随IV变化。这一发现以及aCOP系列的平均缠结长度恒定这一事实表明，we,y（与临界平面应变韧性值相关）可能取决于缠结网络。通过观察到将试样在高于玻璃化转变温度（Tg）下退火后塑性区完全恢复，这一假设得到了合理的解释。回想一下，在冷拉伸（即低于Tg的变形）情况下的形状恢复是由无定形聚合物中的初始缠结网络结构控制的。
SummaryThe plane-stress fracture toughness of amorphous copolyester (aCOP) sheets of different intrinsic viscosity (IV) was determined by the essential work of fracture (EWF) concept using tensile-loaded deeply double-edge notched (DDEN-T) specimens. It was found that the specific essential work of fracture (we) is a composite parameter: its constituents are relied on yielding (we,y) and necking (we)/ respectively. The we values, and especially we,y did not change as a function of IV. This finding along with the fact that the mean entanglement length of the aCOP series was constant, suggest that we,y (which is related to the critical plane-strain toughness value) is likely dependent on the entanglement network. This assumption was reasoned by the observation that the plastic zone was completely recovered after annealing the specimen beyond the glass transition temperature (Tg). Recall that the shape recovery in case of cold-drawing (i.e. deformation below Tg) is controlled by the initial entanglement network structure in amorphous polymers.